The definition given here covers RF (Rzeppa fixed) joints, DO (double offset) plunging joints and VL (Verschiebegelenk Lobro) plunging joints, each having an axial stop for the ball cage. Joints of this type are described in detail under the respective headings in "Gelenke und Gelenkwellen" by F. Schmelz et al, Springer-Verlag, Berlin, etc. 1988. The above-mentioned joints have one feature in common, they are fitted such that, with a preassembled joint including the outer joint part, inner joint part and ball cage in predetermined positions, the balls are individually fitted by setting an assembly angle (.alpha..sub.M) which is greater than the maximum operating angle (.alpha..sub.A). This means that the axes of the outer joint part and inner joint part are arranged at an angle relative to one another such that at least one of the ball windows of the cage freely emerges from the outer joint part so that it is possible for a ball to be inserted from the radial outside into the cage window and the respective track of the inner joint part. The assembly angle (.alpha..sub.M) exceeds the maximum operating or working angle (.alpha..sub.A) which is limited such that self acting dismantling of the joint in the reverse order by loosing balls cannot take place.
Whenever the joint is articulated, all balls of the joint, to the extent that their centers are not positioned on an axis extending perpendicularly relative to the plane of articulation, are circumferentially displaced relative to an assumed central axis (X.sub.n) of their cage window bisecting the circumferential length. This means that when the joint rotates in an articulated condition, the individual balls carry out an oscillating movement in their respective ball windows in the longitudinal direction i.e. in the circumferential direction of the cage. The length of the ball windows is dimensioned such that the above-mentioned articulation can be achieved for fitting all balls.
The fracture strength of ball joints is largely determined by the fracture strength of the ball cage. In particular, the webs between the windows, which are limited by the above-mentioned assembly requirements, constitute the weakest points. Requested large joint operating angles require correspondingly large assembly angles the size of which is limited in view of the reduced web width resulting from larger windows. The strength requirements regarding the width of the webs between the windows also do not allow a desirable increase in the size of the balls with a certain joint size for the purpose of increasing the torque capacity.